I made a custom Uno shield. It breaks out every I/O pin with 5v and GND next to it and accepts a variety of connectors. : r/arduino
KTS 2pcs 8.8x13.6cm DIP Universal SMD DIP SOT Circuit Board pcb platine stripboard veroboard circuit board Prototyp - - Amazon.com
HIFI Class A Power Amplifier Preamplifier Reference Marantz SA17SI Line High Fidelity Headphone Amplifier Board|Operational Amplifier Chips| - AliExpress